re-wrap actions group to support responsive behavior

src/containers/ReviewModal/ReviewActions.jsx

@@ -28,11 +28,13 @@ export const ReviewActions = ({
         <StatusBadge className="ml-3 review-actions-status" status={gradeStatus} />
       </span>
       <ActionRow.Spacer />
-      <Button variant="outline-primary" onClick={toggleShowRubric}>
-        {showRubric ? 'Hide' : 'Show'} Rubric
-      </Button>
-      <Button variant="primary" iconAfter={Edit}>Start Grading</Button>
-      <SubmissionNavigation />
+      <div className="review-actions-group">
+        <Button variant="outline-primary" onClick={toggleShowRubric}>
+          {showRubric ? 'Hide' : 'Show'} Rubric
+        </Button>
+        <Button variant="primary" iconAfter={Edit}>Start Grading</Button>
+        <SubmissionNavigation />
+      </div>
     </ActionRow>
   </div>
 );

src/containers/ReviewModal/ReviewModal.scss

@@ -24,6 +24,10 @@
   .review-actions-status {
     margin-left: map_get($spacers, 3);
   }
+  .review-actions-group {
+    margin-left: 0;
+    flex-shrink: 0;
+  }
 }
 .review-modal-body {
   background-color: $gray-300 !important;

src/containers/ReviewModal/index.jsx

@@ -10,7 +10,6 @@ import {
 
 import selectors from 'data/selectors';
 import actions from 'data/actions';
-import thunkActions from 'data/thunkActions';
 
 import ResponseDisplay from 'components/ResponseDisplay';
 import Rubric from 'containers/Rubric';